Usual devices for embossing foils for the purpose mentioned above, comprise one metallic roller having a toothed hardened surface which is urged against a second roller having a smooth soft coating of plastic material into which parts of the foil passed between the rollers are pressed and embossed. However, such devices have a number of drawbacks. The soft coating of the second roller is rapidly worn and has to be frequently replaced and overhauled, a complicated procedure necessitating long shut-down periods of the machine. The embossing of the foil is not fully satisfactory. Further, the rollers have to be driven in accurate synchronism which requires mutual coupling of the rollers by means of separate gears whereby exchange of worn rollers is rendered more complicated. Moreover, the synchronizing gear between the rollers renders adjustment of the mutual position of the rollers complicated or impossible. It is thus difficult or impossible to properly adjust the pressure between the rollers either initially or later during operation of the device to an optimum value.
In some cases the embossing relief of a steel roller is transfered to a roller coated with thermoplastic material for forming thereon a negative of the relief of the steel roller. These rollers are then used together as a pair of rollers for embossing thin metal foils (French patent No. 1,540,958). However, the drawbacks mentioned above similarly apply for this system in which the roller having a coating of thermoplastic material is rapidly worn. When the pair of rollers is used for embossing a foil passing between them, a synchronizing gear has to be provided between the rollers as set out above.